1. Field of the Invention
The present invention generally relates to a mounting device of an optical unit consisting of two optical components, and more particularly to a mounting device of the type for effecting mounting of one of the two optical components on the other by relative rotation of mating seating and mounting faces of the two optical components (of, e.g., bayonet type), wherein in the seating face of the one optical component is formed a recess which is engaged by an engaging member of the other optical component urged to constantly project beyond the mounting face when the former is properly mounted on the latter.
2. Description of the Prior Art
A conventional mounting device of an optical unit consisting, for instance, of a camera body and an interchangeable lens, essential parts of which are shown enlarged in FIG. 1 with the front wall plate of the former as A and the latter conceptually as B, is provided with an engaging member such as a positioning member for positioning both components in proper mounted relationship and an electrode for electric signal transmission between the two components.
The engaging member C is urged to project beyond the mounting face D on the camera body side and is engaged in a recess F formed in an annular seating face E of the interchangeable lens B when the lens B is properly mounted on the front wall plate A of the camera body. It serves to achieve predetermined functions such as mutual positioning of both optical components and transmission of signals therebetween.
When the interchangeable lens B is turned relative to the front wall plate A of the camera body for mounting on or demounting from the latter by engagement or disengagement of bayonet pawls G and H on B and A sides, the annular seating face E is required to be pressed on the mounting face D. To this end, it is necessary during the mounting or demounting operation to continuously press the annular seating face E of the interchangeable lens B on the mounting face against the positioning member C which is urged by the force of a spring loaded inside the camera body. In this case, as the recess F is formed only at a given angular position on the annular seating face E as shown in FIG. 1 and FIG. 2, hard sliding contact takes place between the annular seating face and the positioning member C with resultant risk of damage to both and, moreover, an unpleasant feel to the user when mounting or demounting the interchangeable lens B. Especially the mounting operation involving engaging the bayonet pawls G and H one another (rotation of the interchangeable lens B in the direction indicated by the arrow in FIG. 2) cannot be accomplished unless the interchangeable lens B is pressed against the front wall plate A of the camera body with sufficient force to overcome the force urging the positioning member C outward, i.e., to bring the mating mounting and seating faces D and E into close contact. If the mounting operation described above is proceeded with forcibly with a pressing force not enough to overcome the urging force, there occurs a risk of the bayonet pawls G and H failing to engage properly, resulting in damage caused to both. Thus, mounting an interchangeable lens on a camera body used to be by no means easy, requiring great care not to cause damage to either or both components of the camera.
With an auto-focus camera (not shown) of the type as described in a co-pending U.S. patent application Ser. No. 366,323, filed on Apr. 7, 1982 and entitled "Interchangeable Type Optical Unit in Optical System" (assigned to the same assignee), now U.S. Pat. No. 4,449,807 a camera body has in it a driving means for focusing the lens system of the interchangeable lens B with its driving shaft arranged to transmit a driving force to a focusing mechanism in the interchangeable lens B through a driven mechanism in the lens for cooperation with the engaging member C and the driving shaft. With such a construction, engaging member C is subjected to a still larger urging force required to ensure unfailing engagement of the driving shaft with the driven mechanism on the lens B side and ensure transmission of the driving force thereto, hence the engaging member is urged more forcefully to project beyond the mounting face D and the above-mentioned problem becomes more marked.